The present invention pertains to frequency discriminator circuitry which provides an output signal that is a linear function of the frequency of an input signal and which is independent of amplitude fluctuations of the input signal. Because frequency discriminators generally have a limited range over which they are linear, variations in the amplitude of input signals can produce nonlinear responses therein. To eliminate this problem prior art discriminators generally require the use of a limiter in the path of the input signal. This solution is unsatisfactory, particularly at microwave frequencies. AGC loops and limiters prior to the discriminator circuitry do not allow for variations between the AGC loop or limiter and the discriminator or for variations in the discriminator itself.